What influences patients' opinion of remission and low disease activity in psoriatic arthritis? Principal component analysis of an international study

Objective. In PsA, the treatment objective is remission or low disease activity (LDA), but patients' perception of remission is poorly studied. This analysis aimed to identify factors associated with patient-defined remission. Methods. This analysis uses ReFlaP data, an international PsA study, with remission defined as 'At this time, is your psoriatic arthritis in remission, if this means: You feel your disease is as good as gone?'. Variables associated with, first, patient-defined remission and, second, LDA were identified using multivariable logistic regression and principal component analysis (PCA) to explore correlated variables. Results. Of 424 patients (50.2% male, mean age 52 years) with established disease, 94 (22.2%) reported themselves as being in remission and 191 (45.0%) as LDA alone. In multivariable analysis pain, psoriasis, impact of disease, physician opinion of symptoms from joint damage and Groll comorbidity index were independent predictors of remission. For LDA, results were similar. Using PCA, variance explained was 74% by five components for men and 80% by six components for women. The key component from PCA for remission was, for both sex, disease impact (Psoriatic Arthritis Impact of Disease, pain and HAQ) explaining 22.2-27.5% of variance. Other factors included musculoskeletal disease activity, chronicity/joint damage, psoriasis, enthesitis and CRP. For LDA, similar factors were identified but the variance explained was lower (64-68%). Conclusion. Many factors impact on patients' opinion of remission, dominated by disease impact. Disease activity in multiple domains, chronicity/age, comorbidities and symptoms due to other conditions contribute to a robust model highlighting that patient-defined remission is multifaceted.